1. Field of the Invention.
This invention relates to reconfigurable registers where a control bit determines the register's mode. In particular, this invention relates to the use of such registers in integrated circuit self-test applications.
2. RELATED ART
Reconfigurable registers are typically digital shift registers wherein control signals select among several possible configurations. For example, the register may be configured to serially shift data, support a normal functional operation or reset. Control logic associated with one or more reconfigurable registers is often used to decode the mode select signals. Control bits are used to encode the mode select signals and control lines couple these control bits to the various reconfigurable registers. Typically, the control bits are located on the periphery of a chip with extended control lines added primarily to couple the control bit to the proper register.
As monolithic integrated circuit chips become more complex, efficient chip topography becomes imperative, and a reduction in control lines, particularly extended control lines, is highly desirable.
Heretofore no reconfigurable register has been available which significantly reduces the register's dependence on such control lines. Furthermore, with the increase in chip complexity, self-test features are increasingly in demand, and reconfigurable registers play a central roll in many self-test schemes. Thus, reconfigurable registers which enhance chip topography also advance self-test design.